Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Felsite

A general term for light-colored, fine-grained volcanic rocks rich in quartz and feldspar, like rhyolite.

Also called Sci-Fi Jasper, a Mexican jasper-rhyolite with swirling abstract patterns in cream, tan, gray, pink, and green.

A fine-grained volcanic rock intermediate between andesite and rhyolite, common at explosive stratovolcanoes.

A mottled green jasper whose blotchy spotting resembles frog skin, valued by lapidaries for its earthy, camouflage-like patterns.

A high-temperature potassium feldspar that forms glassy crystals in fast-cooled volcanic rocks, sometimes cut as a moonstone gem.

A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.

A nodular rhyolite geode-like ball whose plain exterior hides a star-shaped agate or chalcedony core when cut.

A rare Indonesian jasper from Sulawesi known for ghostly tube structures, brecciated patterns, and contrasting grey, red, and purple zones.

A black metallic manganese iron oxide famous for sharp cubic crystals, classically found with red beryl and topaz in Utah rhyolite.

A fine-grained, intermediate volcanic rock common at subduction-zone volcanoes, between basalt and rhyolite in composition.